This invention relates to a gas regulator/valve device, particularly for use with breathing apparatus.
Known breathing apparatus generally comprises a source of breathable gas, such as a cylinder of compressed air, some form of hood or mask which is placed over the user's face or head and a tube connecting the two to supply gas from the source to the hood or mask. Generally speaking, the source of gas will be under a higher pressure than is necessary for supply to the user, and a regulator is used at the output of the gas source to reduce the pressure from that of the cylinder to that required by the user. Finally some form of valve is used to allow the supply to be turned on and off.
As the gas cylinder empties, the high pressure within the cylinder gradually falls until the pressure within the cylinder is no greater than the output pressure from the regulator. At this point, the cylinder can be considered to be virtually empty, and requires charging. In certain applications, it is useful to provide a warning to the user that the cylinder is near-empty, or to initiate some automatic process for charging cylinders. For example in emergency escape breathing apparatus, the user has a very limited supply of gas, usually from just a single cylinder, so there is no question of changing the cylinder and carrying on. Rather, the purpose of such equipment is to allow the user, after donning the equipment, to escape to safety from a dangerous situation. In such circumstances, it may be vital to know that the cylinder is running out.
It is known, in these circumstances, to provide an audible warning, this typically being in the form of a whistle actuated by the gas supply. Such whistles are generally connected to the cylinder side of the regulator and thus monitor the high cylinder pressure. Means are provided, within the whistle body, for detecting when the cylinder pressure falls to a predetermined level, at which point a valve is opened to actuate the whistle by means of the remaining gas pressure. Such whistles are complicated and expensive.
Known regulators comprise a piston which is movable within a cylindrical bore and controls flow through an orifice at the output from the cylinder to regulate the supply from the cylinder.